Optical recording elements for recording and storing digital information are known. One of the currently popular optical recording element is the compact disc or CD. CDs and recordable CDs (CD-Rs) have transformed the personal entertainment, personal computer and data storage industries. CDs and CD-Rs have made it possible to store enormous amounts of music or data on inexpensive, reliable, mass produced media.
Digital Versatile Disc (DVD) and recordable DVD (DVD-R) optical recording elements are being developed. These elements have significantly greater storage capacity than CDs.
In CDs and DVDs digital information is stored in the form of low reflective marks on an otherwise reflective background. In this format the optical information is in the form of read only memory or ROM. Optical information is not recorded in real time, but is produced by press molding. In a typical process a substrate is stamped with a master containing the digital information in an embossed form. The stamped substrate, beaing deformations caused by the embossed master, is coated with a reflective layer and then with a protective layer. In the stamped substrate areas having the deformations the reflectivity is lower than in undeformed areas.
Several different layer configuration embodiments are possible for DVD optical recording elements. Two embodiments are presented in FIGS. 1 and 2.
In the FIG. 1 embodiment the DVD element comprises the following layer arrangement:
(a) a transparent substrate that may or may not include grooves for laser tracking;.(1) PA1 (b) an optical recording layer; (2) PA1 (c) a light reflecting layer (3). PA1 (d) a protective layer (4). PA1 (e) an adhesive layer (5). PA1 (f) a protective layer (6). PA1 (g) a reflective layer (7). and PA1 (h) a substrate (8). PA1 (a) a transparent substrate that may or may not include grooves for laser tracking (1); PA1 (b) an optical recording layer; (2) PA1 (c) a light reflecting layer (3). PA1 (d) a protective layer (4). PA1 (e) an adhesive layer (5). PA1 (f) a protective layer (6). PA1 (g) a reflective layer (7). PA1 (h) an optical recording layer; and PA1 (i) a transparent substrate that may or may not include grooves for laser tracking. PA1 (a) a transparent substrate; PA1 (b) an optical recording layer; PA1 (c) a light reflecting layer; PA1 (d) a polymeric protective layer of one or more vinyl monomers, including at least one vinyl monomer having incorporated therein a amine group that accelerates curing of cyanoacrylate adhesives. PA1 (e) a cured cyanoacrylate adhesive; and PA1 (f) a substrate. PA1 providing a first assembly comprising: PA1 providing a second assembly comprising at least a substrate; PA1 forming a laminate of the first and second assembly by bonding, with a cyanoacrylate adhesive, the protective layer of the first assembly to (i) the substrate of the second assembly or (ii) another exposed layer of the second assembly.
In the embodiment presented in FIG. 1 one or more of layers (d), (f) and (g) may be omitted in some applications.
In the FIG. 2 embodiment the DVD element comprises the following layer arrangement:
In some FIG. 2 embodiments one or both of the protective layers (d) and (f) may be omitted.
An important component in these multilayer laminate DVD elements is the adhesive layer. The adhesive must be effective in holding the various layers together in a single package in a variety of environments. In embodiments having two recording layers the adhesive layer must be optically clear at the read and write wavelengths. Rapid curing of the adhesive is desirable to avoid warping of the element.